Editor's note: This article was written in August
1978, initially published in The Brass Bulletin, and reprinted by the
Schilke Company in connection with the promotion of the tunable bell
trumpets being manufactured by the company. It was distributed at
clinics and conferences.

Dr Colin Bloch is an Architect in Bristol, UK, where he plays
in orchestras and as a recitalist. He has been playing Schilke since
1977 and latterly Monette. He can be emailed at
cb6681@yahoo.co.uk.

The bell-tuned, or tuning-bell trumpet, is a relatively recent
development in trumpet technology and design. It is the purpose of
this article to demonstrate the efficiency of this innovation in
improving overall intonation.

By bell-tuned trumpets, we mean those whose main intonational
adjustment is made at the junction of the bell and the valve cluster,
as opposed to the more conventional methods of using either a tuning
slide, or a tuning shank fitted into the leadpipe.

The initial section of the trumpet tubing, from the mouthpipe to
the valve cluster, is of critical importance in determining the
intonational characteristics, timbre and response of the instrument.
This represents a length of approximately 46 cm on the C trumpet, and
it is important that it be smooth and uninterrupted along its entire
length.

We normally find three interruptions along this section of tubing.
Two occur at the sudden change in diameter caused by the tuning
slide. The third is caused by the aperture to the waterkey.

The waterkey in itself is a relatively minor problem, and can be
designed out either by using the cylindrical type 'Amado' waterkey;
by using a studded waterkey with a nipple on the rubber which fits
flush with the inside of the tubing when closed; or more simply by
having no waterkey at all and emptying the instrument by inversion,
as on the french horn.

It might appear that such a small change in the diameter of the
inside tubing, as caused by the extension of the tuning slide, should
have no noticeable effect. This is a fallacy. Intonational distortion
is caused by the fact that various notes of the differing harmonic
series tend to 'focus' at different points along the length of this
critical section of tubing. The resultant effect can best be likened
to the turbulence in a water pipe at any point where the diameter
might change.

A series of test was carried out on a bell-tuned trumpet, which
also has a tuning slide, to determine the efficiency of the
bell-tuned system, as compared to the tuning-slide. The tuning slide
is included on the instrument to facilitate cleaning and to allow the
insertion of slides of another key. The first trumpets built with
tuning-bells had no main tuning-slide.

The instrument used for the tests was C trumpet, with an XL bore,
fitted with a beryllium bronze bell. (This lightweight bell has no
significant effect on intonation its purpose being to improve
response and projection. Tests have shown that over a given distance
a drop in sound level of 5% was recorded, compared to 12% for a brass
bell.)

In order to keep the tests as accurate as possible, various
factors had to be kept constant for both the bell-tuned and the
slide-tuned tests. These include:

the tuning standard (A = 442.5 Hz)

the test player

the mouthpiece (Schilke #20)

No adjustments were made to the three minor tuning slides, and
they were all kept in throughout both test sequences.

It is important when examining the results of these tests to
remember that it is essentially a comparative test, and that the two
graphs do not necessarily indicate a tuning pattern for the
instrument, as this to a large extent would depend on the player and
his physical and musical characteristics. The essence of the results
lies in the difference between the two graphs.

The range chosen was F-sharp to F-natural, encompassing some 36
notes. Each note was blown as a long note, then 'bent' up and down
until the test player lost all precept of pitch. This note was then
'centered' until it was felt that the maximum number of overtones
were being generated, and a reading was taken on an electronic tuner.
This was done five times, over an extended period, for each test. The
two graphs thus represent the result of some 360 readings.

Where alternate fingerings were available, those producing the
most favorable results were used. The only deviations were that
middle and top E-flat were fingered 2 and 3, and middle E open. (Some
C trumpets require this note to be played on 1 and 2.) On the
slide-tuned test, middle D was found to be better in tune on 1 and 3
than on 1.

The following facts derived from the test results, may be of
interest:

On the slide-tuned trumpet the average deviation was 8.57
cents, compared to only 6.96 cents on the bell-tuned trumpet,
representing a difference of 35.09 percent (there are 100 cents to
the semi-tone).

On averaging out the whole range of the test with reference to
the tuning standard, the slide-tuned trumpet was found to be .04
cents flat. The bell-tuned trumpet yielded the far more preferable
figure of 0.03 cents sharp.

On the slide-tuned trumpet the usual tuning notes of A and
B-flat were significantly out of tune, the A being 2.57 cents
sharp, and the B-flat being 6.43 cents sharp. On the bell-tuned
trumpet these notes were each less than 0.5 cents sharp.

It should in all fairness be mentioned that there are certain
disadvantages attached to the bell-tuned trumpet:

There are of necessity no cross braces to the bell, making the
instrument more susceptible to damage.

Quick tuning adjustments are difficult, as two screws have to
be tightened and loosened.

It can thus be established that the tuning-bell system has the
following range of advantages to offer over the conventional trumpet:

A significant decrease in intonational deviation over the
whole range.

More accurate tuning notes ( A and B-flat) relative to the
tuning standard.

Although not necessarily an advantage, the tuning-bell is more
sensitive, requiring an extension of 17.6 mm on average, compared
to 26.6 mm for the tuning slide.

The bell is detachable and can thus be alternated with bells
of differing pitch, when using the corresponding tuning slides.

The bell can be used when attached only at the bell stud, so
that it stands free and is not dampened by contact with either the
rest of the instrument or the hands of the player.

It is hoped that this article has demonstrated some of the
advantages associated with the tuning-bell system, and has also
served to dispel any doubts which might exist as to its value.